Any tips or something usful?

pray to god

Focus on making your core game simple then decide to add anything complex to you and leave a day or 2 to clean bugs.

me too, we're in the same boat. But I have a team member with less experience than I do so idk how this will turn out

Write all your thoughts on the theme down, even if you absolutely hate them. You'll be able to connect different ideas into one nice concept.